The research is designed to examine the neurotransmitters which are responsible for the postsynaptic inhibition of alpha motoneurons of the lumbar spinal cord during the behavioral state of active sleep. Combined intracellular recording and iontophoretic ejection experiments will be conducted on unanesthetized, undrugged, intact cats during states of sleep and wakefulness. These experiments entail a determination of the neurotransmitters that are involved in various spontaneously-occurring and reticular-induced patterns of postsynaptic inhibition of spinal cord motoneurons during active sleep. The proposed studies should (1) identify the neurotransmitters underlying the different spontaneous patterns of postsynaptic inhibition of lumbarmotoneurons that are present durin the non-rapid eye movement and the rapid eye movement periods of active sleep, (2) identify the neurotransmitters that are involved in th postsynaptic inhibition of lumbar motoneurons that is induced by the nucleus pontis oralis and the nucleus reticularis gigantocellularis during these periods of active sleep, and (3) provide a new experimental paradigm for studying neurotransmitters mediating behavioral process from an intracellular perspective utilizing iontophoretic techniques in the chronic animal.